Numerical modelling of radiative heat transfer in an internal indirect reforming-type SOFC

The present paper describes numerical modelling of the radiative heat transfer process in the module chamber of an internal indirect reforming-type SOFC. The ability to do internal reforming is one of the characteristics of high-temperature fuel cells, SOFC. As in any high-temperature system, radiative heat transfer is important. In this article, heat transfer between the fuel reformer surface and all other surfaces facing the reformer surfaces is modelled. Governing equations for radiative heat transfer are described using Hottel's zone method. The resulting radiation–conduction conjugate heat transfer problems are numerically solved with a combination of Gauss–Seidel and Newton–Raphson methods. The steam reforming reaction occurring inside the fuel reformer is described using Achenbach model. The obtained results indicate that, for the development of effective indirect internal reforming, the position of the reformer in the module chamber and emissivity of the surfaces of the reformer, cell and other elements in the SOFC module all play a key role.     

Three-dimensional modeling of the I-TevI homing endonuclease catalytic domain, a GIY-YIG superfamily member, using NMR restraints and Monte Carlo dynamics

Using a recent version of the SICHO algorithm for in silicoprotein folding, we made a blind prediction of the tertiarystructure of the N-terminal, independently folded, catalyticdomain (CD) of the I-TevI homing endonuclease, a representativeof the GIY–YIG superfamily of homing endonucleases. Thesecondary structure of the I-TevI CD has been determined usingNMR spectroscopy, but computational sequence analysis failedto detect any protein of known tertiary structure related tothe GIY–YIG nucleases (Kowalski et al., Nucleic AcidsRes., 1999, 27, 2115–2125). To provide further insightinto the structure–function relationships of all GIY–YIGsuperfamily members, including the recently described subfamilyof type II restriction enzymes (Bujnicki et al., Trends Biochem.Sci., 2000, 26, 9–11), we incorporated the experimentallydetermined and predicted secondary and tertiary restraints ina reduced (side chain only) protein model, which was minimizedby Monte Carlo dynamics and simulated annealing. The subsequentlyelaborated full atomic model of the I-TevI CD allows the availableexperimental data to be put into a structural context and suggeststhat the GIY–YIG domain may dimerize in order to bringtogether the conserved residues of the active site.     

Defect Chemistry of (La,Sr)MnO3

Defect-disorder models are derived for undoped and strontium-doped LaMnO₃. A random-defect model and a cluster-defect model are both considered within the regimes that correspond to oxygen deficit and oxygen excess. The models are constructed based on the experimental nonstoichiometry data that was reported by previous researchers. According to both models, the addition of strontium leads to an increase of the concentration of electron holes and oxygen nonstoichiometry. The defect clusters that are predicted by the cluster model have a marked concentration only at very low oxygen partial pressures. Both models are verified against the electrical-conductivity data. A good agreement between the random-defect model and the experimental data is shown.     

Solid-state spun fibers and yarns from 1-mm long carbon nanotube forests synthesized by water-assisted chemical vapor deposition

We report continuous carbon nanotube (CNT) fibers and yarns dry-drawn directly from water-assisted chemical vapor deposition (CVD) grown forests with about 1-mm height. As-drawn CNT fibers exist as aerogel and can be transformed into more compact fibers through twisting or densification with a volatile organic liquid. CNT fibers are characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, Raman microscopy, and wide-angle X-ray diffraction. Mechanical properties and electrical conductivity of the post-treated CNT fibers are investigated. The resulting fibers show the work of rupture of 30 J/g and DC electrical conductivity of 5.0 × 10⁴ S/m.     

Reconstruction of nonuniformly sampled images in spline spaces.

This paper presents a novel approach to the reconstruction of images from nonuniformly spaced samples. This problem is often encountered in digital image processing applications. Nonrecursive video coding with motion compensation, spatiotemporal interpolation of video sequences, and generation of new views in multicamera systems are three possible applications. We propose a new reconstruction algorithm based on a spline model for images. We use regularization, since this is an ill-posed inverse problem. We minimize a cost function composed of two terms: one related to the approximation error and the other related to the smoothness of the modeling function. All the processing is carried out in the space of spline coefficients; this space is discrete, although the problem itself is of a continuous nature. The coefficients of regularization and approximation filters are computed exactly by using the explicit expressions of B-spline functions in the time domain. The regularization is carried out locally, while the computation of the regularization factor accounts for the structure of the nonuniform sampling grid. The linear system of equations obtained is solved iteratively. Our results show a very good performance in motion-compensated interpolation applications.     

Synthesis and characterization of carbonaceous replicas of multilayered vesicular siliceous materials

Synthesis of novel, carbon porous replicas of vesicular siliceous materials has been described. The original siliceous materials consist of small, spherical structures resembling onions, known in the literature as multilamellar vesicles (MLVs). They have been characterized with a number of analytical methods that allow one to determine its 3-D structure and basic parameters of the pore system. Carbonaceous materials, made similarly of onion-like porous structures, have been obtained using a standard procedure to form replicas. They have been characterized by the same methods as those applied to the parent materials.     

The impact of a sewage treatment plant's effluent on sediment quality in a small bay in Lake Geneva (Switzerland–France). Part 2: Temporal evolution of heavy metals

The Bay of Vidy is the most contaminated area of Lake Geneva, Switzerland, as a result of the release of treated and untreated waste water from the municipal sewage treatment plant of the city of Lausanne and its surroundings. The reconstruction of the historical deposition of heavy metals in the sediment of the bay has been performed by the analysis of several dated (radiocaesium) sediment cores. The presence of sewage‐derived contaminants in the Bay of Vidy since the beginning of the sewage treatment plant's operations in 1964 is clearly observed, when a sharp increase in heavy metal contents is recorded, with maximum concentrations of cadmium, copper, zinc and lead occurring between the late 1960s and early 1970s. Despite considerable improvement in recent times, the present concentrations of the investigated heavy metals in sediments of the Bay of Vidy are still higher than concentrations measured at the centre of the lake, the latter close to Lake Geneva's natural background values. It is concluded that the quantity of heavy metals deposited in the bay is considerable and, because of sediment instability, will constitute a potential hazard for biota.     

Interfacial reactions of Sn–Zn–Ag–Cu alloy on soldered Al/Cu and Al/Al joints

This work shows the effect on the soldering process of the addition of Ag and Cu to Sn–Zn alloys. Soldering of Al/Cu and Al/Al joints was performed for a time of 3?min, at a temperature of 250°C, with the use of flux. Aging was carried out at 170°C for Al/Cu and Al/Al joints for 1 and 10 days. During the aging process, intermetallic layers grew at the interface of the Al/Cu joint at the Cu substrate. Intermetallic layers were not observed during wetting of Al/Al joints. On the contrary, dissolution of the Al substrate and migration of Al-rich particles into the bulk of the solder were observed. The experiment was designed to demonstrate the effect of Ag and Cu addition on the dissolution of Al substrate during the soldering and aging processes. In the solder alloys, small precipitates of AgZn₃ and Cu₅Zn₈ were observed.     

Suspension flow in crystallizers with and without hydraulic classification

The main goal of this paper is to model a multiphase flow of a monodispersed suspensions in various types of crystallizers: Draft Tube Magma (DTM), Double Draft Tube (DDT) and Fluidized bed (FL). To do this, the CFD (Computational Fluid Dynamics) methods were used. The geometry of model apparatus was similar to those applied in industry. The composition of suspensions and their physical properties were the same as in practical cases.     

Emulsion Properties and Phase Equilibrium and of New Asymmetric Gemini Surfactants Consisting of Fatty Acid Esters of Polyethoxylated Alcohol or Phenol

The emulsion and phase properties of water-surfactant systems are reported for nonionic surface active compounds of the asymmetrical gemini type resulting from the esterification of a polyethoxylated alcohol and a fatty acid. These products exhibit typical gemini surfactant properties, in particular, low critical micelle concentration (CMC) and good emulsifying properties, and they often form a gel depending on the temperature and concentration.